The present invention relates to a method for eliminating the lactose contained in whey and/or wheyey residues and waste in order to then extrapolate proteins therefrom so that said proteins constitute a product which is reusable and in particular generally digestible. Another aspect of the invention relates to the plant stages for performing this elimination at the cellular level. Another aspect of the present invention relates to the processing of whey and/or wheyey residues, comprising lactose elimination to be able to recover the proteins of interest. Finally, another aspect of the invention is the use of particular microorganisms which perform the elimination, at the cellular level, of the lactose contained in whey and/or wheyey residues.
The need to produce proteins to be added to fodder used in intensive livestock rearing is a serious problem, since obtaining noble proteins is becoming increasingly onerous. In recent times there has been a decrease in the availability of fishmeal and meatmeal flours owing to limited exports from foreign countries.
Furthermore, the conditioning of dairy industry waste per se is a cost which affects the community without often providing the expected environmental result, since the proposals for disposal do not always fully solve the problem.
It is therefore clear that the extrapolation of proteins is an environmental problem as well as an economical one and that the possibility to obtain these proteins from the wastewater of agri-foodstuff industries, from slaughterhouse waste, from plant wastewater and from other sources in general is highly important.
Currently, the technologies related to the whey disposal process can be classified as follows:
I. Demineralization with Ion-exchange Resins
This operation is performed with the aid of ion-exchange resins. For a correct metabolization process, as stated in a well-known report from the Animal Disease Prevention Institute of Teramo, treatment must be performed on 50% of the available whey. The removal of these salts allows to recover products meant for agriculture.
II. Recovery of Milk Proteins
Milk proteins are very important in the preparation of baby biscuits, dietary foodstuffs and foodstuffs in is general, but the high cost of the plants and of their management makes the recovery technology, with reverse-osmosis and ultrafiltration processes, feasible only in large dairies or dairy consortia.
III. Recovery of Lactose for Food and Pharmaceutical Use
Lactose is used in many fields, such as the pharmaceutical, cosmetic and agri-foodstuff industry, but its consumption on a national level is rather low and plant costs are rather high.
IV. Drying to Obtain a Powder to be Used in the Fodder Industry
The use of dried whey has no industrial application of interest; new EEC standards have indeed penalized it for two essential reasons: lactic acidity and the presence of lactose.
The lactic acidity of lactose allows to use the product only in a narrow range of foodstuffs and pharmaceutical products, although the use of demineralization has partly corrected this acidity.
However, the decisive factor that makes dried whey not adapted for fodder and for human use, at least in many cases, is the presence of lactose. In order to be metabolized, lactose must in fact be broken down by .beta.-galactosidase, which however is present only in unweaned animals. This means that lactose cannot be digested by animals weighing more than 20-25 kg, which return it intact in their feces. Furthermore, in animals and humans lactose is the triggering factor in a very severe hereditary-type disease known as galactosemia. Clearly, potentially galactosemic humans and animals cannot include lactose-containing food in their diet.
In view of the above described problems, there is the need of eliminating the lactose contained in whey in order to then extrapolate the free proteins therefrom and market a product which is generally more digestible. It is even clearer that it is necessary and advantageous to perform this elimination of lactose before the product that contains it reaches biologically advanced organisms, i.e., to perform it at the cellular level, with all the selective possibilities entailed by this approach.
The normal metabolization of lactose, which is the main sugar contained in whey and/or wheyey residues, is feasible because the above mentioned microorganisms have .beta.-galactosidase activity, which as mentioned breaks down lactose into glucose and galactose.
The strains, however, are inhibited in their growth by the ethyl alcohol produced by the enzyme that catalyzes the first step of biosynthetic pathways (in our case, .beta.-galactosidase). This inhibition, known as "feedback inhibition", is such that when the ethanol levels tend to drop, the .beta.-galactosidase becomes active again.
It is thus evident that it is important to remove the ethanol catabolite in order to obtain a continuous process; one possible route is the symbiosis of two strains of microorganisms, the first one being glucose+galactose+ and the second one being ethanol+. However, this route is not feasible in the context of proteins, since the ethanol+ microorganism is not in the class of "safe" strains. Microorganism strains intended for lactose metabolization must in fact be those classified as "safe" and proposed and accepted by the EEC and CNR commissions covering this issue. However, it is noted that this symbiosis, which is widely studied in the laboratory, remains highly interesting in fields in which the biomass is meant for agricultural products.
The mechanism for lactose metabolization generally follows three routes:
1. The lactose is broken down by an extracellular enzyme (.beta.-galactosidase) into glucose and galactose by a glucose+ and galactose+ microorganism in order to act on its endocellular metabolism (as explained above); PA1 2. The lactose is brought into the cell by means of a carrier protein activated by the enzyme permease; the endocellular hydrolytic breakdown releases glucose and lactose, which enter the tricarboxylic acid cycle by means of the Embden-Meyerhoff route; PA1 3. A hydrolytic breakdown of the lactose is performed by enzymes by means of trapped cells and the resulting saccharides are metabolized with at least one pair of hyphomycetes in which one is glucose+galactose- and the other is glucose-galactose+.